1. Field of the Invention
The disclosed embodiments of the present invention relate to a switching regulator, and more particularly, to a ripple-based control switching regulator and related a ripple-based control switching regulating method.
2. Description of the Prior Art
A ripple-based control switching regulator can feedback an output voltage cross a filter capacitor in real time and determine whether to charge an inductor or discharge the inductor accordingly. When a feedback output voltage is lower than a predefined reference voltage, the ripple-based control switching regulator will charge the inductor by turn on an up-bridge transistor and turn off a down-bridge transistor for a fixed on time, so as to increase the output voltage of the switching regulator. When the on time is over, and the feedback output voltage is higher than the predefined reference voltage, the ripple-based control switching regulator will discharge the inductor by turn off the up-bridge transistor and turn on the down-bridge transistor, so as to decrease the output voltage of the switching regulator.
However, since the filter capacitor has a parasitic inductor, when the switching regulator charges, the parasitic inductor of the filter capacitor will have a positive voltage. On the contrary, when the switching regulator discharges, the parasitic inductor of the filter capacitor will have a negative voltage. Thus, when the on time is over, the positive voltage of the parasitic inductor of the filter capacitor will become the negative voltage instantly, and lower the whole output voltage of the filter capacitor, and the output voltage of the filter capacitor may be lower than the predefined reference voltage again instantly and result in triggering the on time twice in a row (i.e. a double pulse). This will input too much power to the inductor and increase a subharmonic oscillation of the output voltage. Thus, the prior art often measures the inductor current directly but not the voltage of the filter capacitor to avoid the parasitic inductor effect. However, measuring the inductor current directly has higher cost and larger measuring error. Thus, an innovative ripple-based control switching regulator is required to solve the above-mentioned problems.